In a printing apparatus for printing an image by discharging a printing material from a plurality of nozzles in the prior art, a preliminary discharge operation is performed in order to effect the recovery of any nozzles that fail to discharge the printing material properly. The preliminary discharge processing usually is processing that causes a nozzle to forcibly discharge printing material at a prescribed preliminary discharge position. Specifically, failure of a nozzle to discharge is monitored in the printing apparatus and, if a nozzle that fails to discharge for a predetermined period of time is found, the nozzle is moved to the preliminary discharge position and the printing material is forcibly discharged from this nozzle.
In the prior art described above, however, the preliminary discharge processing is executed in the printing apparatus independently and processing for printing images is dealt with entirely separately of processing for preliminary discharge processing. As a consequence, it is necessary to perform preliminary discharge processing through an independent sequence both in terms of hardware and software. The processing load becomes a problem. Further, since whether preliminary discharge processing is necessary or not is determined within the printing apparatus, print processing is delayed by the amount of time needed for the determination processing.
For example, use is made of a timer that measures the time intervals of preliminary discharge within the printing apparatus, or the number of printing scans is counted. If a predetermined period of time or predetermined number of scans is exceeded and image data is received, processing for head recovery is executed. This makes it necessary to execute processing for needless movement of the carriage.